Hi Mike yes, i have seen it once, the efs must be in the same Availability Zone ( if not, you may be charged for data transfer and have some perf degradation .. ) and i think the only downside is that it's network performance , it's less performant that having a local disk. i think it's ok if your use case permit , however if you are planning to use Hbase/Storm where latency is critical , i recommend you to do some benchmarking first. ... View more